a) Field of the Invention
This invention relates to a damper assembly to be disposed between an engine and a transmission, especially to a damper assembly a coil spring of which is protected from permanent setting in fatigue or breakage.
b) Description of the Related Art
In a conventional damper assembly, a driven member is driven via a coil spring by a driving member connected directly to an engine. This conventional construction is accompanied by an unavoidable drawback that due to over-loads applied by combustion in the engine, the coil spring is repeatedly compressed fully with all coils brought into contact with adjacent coils, resulting in permanent setting in fatigue or breakage.
With the foregoing in view, the present invention has as a primary object the provision of a damper assembly a coil spring of which is protected from permanent setting in fatigue or breakage.
According to one aspect of the invention, a damper assembly includes a drive plate, a driven member, a damper mechanism, a stopper mechanism, front and rear covers, and a retainer cover. The is rotatable relative to the drive plate. A damper mechanism includes a spring, a spring seat on the drive plate, and a spring seat on the driven member. The spring is disposed between the spring seat on the drive plate and the spring seat on the driven member. The stopper mechanism includes an engageable portion on the drive plate, and an engageable portion on the driven member. The relative rotation between the drive plate and the driven member is limited by engagement between the engageable portion on the drive plate and the engageable portion on the driven member. The damper mechanism and the stopper mechanism are arranged in the same plane that is normal to an axis of the driven member. The front, rear and retainer covers form a sealed hollow space in which the drive plate, spring, and driven member are disposed. The sealed hollow space is filled with a viscous medium such that viscous damping resistance is applied to the relative rotation between the drive plate and driven member.
In a preferred embodiment of the invention, the engageable portion on the drive plate is arranged on an inner circumference of the drive plate, and the engageable portion on the hub is arranged on an outer circumference of the hub. The engageable portions on the drive plate and hub are brought into engagement with each other by the relative rotation between the drive plate and the driven member.
In another preferred embodiment of the invention, the drive plate has a tab and two engageable portions arranged with a predetermined interval on the tab, and the hub has a tab and two engageable portions arranged with a predetermined interval on the tab.
The damper assembly may further include an intermediate member arranged for relative rotation between the driving member and the driven member and formed integrally with the dividers. The relative rotation between the driving member and the intermediate member via the coil spring is limited by the engagement between one or more engageable portions arranged on the driving member at predetermined locations and one or more of a corresponding first set of engageable portions arranged on the intermediate member at predetermined locations. The relative rotation between the intermediate member and the driven member is limited by the engagement between one or more of a second set of engageable portions arranged on the intermediate member at predetermined locations and the corresponding engageable portions arranged on the driven member at predetermined locations.
Owing to the above-described construction, the coil spring is limited in coil angle whenever a predetermined load or a load greater than the predetermined load is applied. This limitation makes it possible to protect the coil spring from over-loads and hence, from permanent setting in fatigue or breakage without requiring additional parts. With a minimized increase in the manufacturing cost, the coil spring can therefore be protected from permanent setting in fatigue or breakage.
Preferably, the damper assembly may be effectively sealed within a hollow space formed by a front cover and rear cover, which are fixedly secured on the driving member, and a retainer cover plate. The hollow space is filled with a viscous medium such that viscous damping resistance is applied to relative motion between the coil spring and the driven member (and the intermediate member if any). This preferred embodiment makes it possible to effectively reduce wear and noise which occur between the associated members.